The present disclosure relates to a coating method for coating components, in particular for coating motor vehicle bodywork components in a painting installation. The present disclosure also relates to a corresponding coating installation.
In the painting of motor vehicle bodywork components, rotary atomisers which emit a rotationally symmetrical coating medium stream and accordingly generate a rotationally symmetrical spray pattern on the component surface are mostly used as the application device. The angular orientation of such a rotary atomiser in relation to the longitudinal axis of the coating medium stream generally plays no part herein, since the coating medium stream is rotationally symmetrical. Exceptionally, however the angular position of the rotary atomiser can have an effect if the coating medium stream is asymmetrically blown by steering air, which then results in a correspondingly asymmetrical spray pattern on the component surface. Previously, however, no attempt has been made specifically to influence the angular position of the rotary atomiser during operation.
However, other application devices are also known from the prior art (e.g. DE 10 2013 002 412 A1) which apply a coating medium stream that is not rotationally symmetrical and therefore creates a spray pattern on the component surface that is not rotationally symmetrical.
This can be problematic if such application devices are used to coat a component surface in that a plurality of adjacently placed coating paths 1 are applied onto the component surface, as shown in FIG. 7. The coating paths 1 must herein directly abut one another as far as possible without gaps and without overlaps, since the application device emits a rectangular, sharp-edged spray pattern 2. The coating paths 1 therefore have a path course 3 which extends parallel between the adjacently placed coating paths 1 so that the adjacent coating paths 1 abut one another overlap-free and without gaps. However, this leads to problems if the component to be coated is bordered by two component edges 4, 5 that do not extend parallel to one another. Thus, FIG. 7 shows a straight component edge 4 and a curved component edge 5, wherein the coating paths 1 conform to the curved component edge 5, which leads in the region of the other component edge 4 to uncoated regions 6. It should be noted herein that the application device is not rotated during the movement along the path course 3, so that the spray pattern 2 is always oriented with its longitudinal direction 7 perpendicular to the path course 3 and thus parallel to the path transverse direction. This orientation of the spray pattern 2 leads to a maximum path width of the coating path 7.
The problem of the uncoated regions 6 according to FIG. 7 can be solved in that the individual coating paths 1 do not extend exactly parallel to one another, as shown in FIG. 8, wherein in FIG. 8, corresponding details are provided with the same reference signs as in FIG. 7. Thus the lower coating paths 1 are herein curved and conform to the lower component edge 5. Toward the top, the coating paths 1 are then increasingly straight and thus increasingly conform to the upper component edge 4. In this way, the uncoated regions 6 are prevented. However, this leads to overlaps between adjacent coating paths 1 and thereby to overcoated regions 8 with a correspondingly excessive layer thickness, which is also undesirable. Herein also the application device is not rotated during the movement along the path course 3, so that the spray pattern 2 is always oriented with its longitudinal direction 7 perpendicular to the path course 3 and thus parallel to the path transverse direction.
Regarding the general technical background, reference is also made to DE 10 2011 114 382 A1. This document discloses a coating method in which the spray stream is tilted relative to the component surface during the painting in order to compensate for asymmetries. However, this is not useful for the painting of paths which are not exactly rectangular.
It would be desirable to prevent both the uncoated regions 6 and the overcoated regions 8 on such component surfaces when an application device is used which applies a rotationally asymmetrical coating medium stream generating an elongate spray pattern with a particular longitudinal direction.